Method and apparatus for flaring combustible gaseous materials



Feb. 14, 1961 FROST r 2,971,605

METHOD AND APPARATUS FOR FLARING COMBUSTIBLE GASEOUS MATERIALS Filed Feb. 18, 1957 3 Sheets-Sheet 1 John P. Longwel! Hoyt C. Hoffe! Inventors Edward E. Frost B Attorney E. E. FROST EIAL 2,971,605 METHOD AND APPARATUS FOR FLARING COMBUSTIBLE GASEOUS MATERIALS Feb. 14, 1961 3 Sheets-Sheet 2 Filed Feb. 18, 1957 John F! Longwell Hoyt C. Hofiel Inventors Edward E. Frost By Attorney E. E. FROST ETAL 2,971,605 METHOD AND APPARATUS FOR FLARI COMBUSTIBLE GASEOUS mum.

Feb. 14, 1961 3 Sheets-Sheet 3 Filed Feb. 18. 1957 John P. Longwell Hoyt C. Hottel Inventors Edward E. Frost ByWW Attorney United States Patent METHOD AND APPARATUS FOR FLARING COMBUSTIBLE GASEOUS MATERIALS Edward E. Frost, San Diego, Calif Hoyt C. Hottel, Winchester, Mass, and John P. Longwell, Westfield, NJ., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Feb. 18, 1957, Ser. No. 640,749

12 Claims. (Cl. 183-6) The present invention relates to an improved method and apparatus for flaring combustible gaseous materials wherein combustion and burning of such materials is accomplished substantially without air pollution by smoke. The invention further relates to an apparatus and method of flaring such materials substantially without producing a flame visible in any direction except from substantially directly above the zone of combustion. The invention relates especially to a method and means for flaring and burning gaseous hy ocarbon materials and particularly such materials as derived from operations for the refining of petroleum oils in many industrial operations, and particularly in the refining of petroleum oils, large volumes of combustible gaseous materials are produced. Some of these materials have no real economic value as fuel or otherwise and must be disposed of. Additional such materials results from upset conditions in the normal operation of a refinery wherein gases which ordinarily might be subjected to further processing in order to obtain valuable products must be vented in order to avoid the occurrence of dangerously abnormal pressures in operating equipment. The total volume of all such accumulations of gases in normal refinery operation, and the hazardous nature thereof make it impossible for such gases to be discharged directly into the atmosphere. In practice, therefore, it is customary to burn such gases as they are discharged from an exhaust or flare stack at a considerable distance above the ground, although on occasion for the sake of economy, burning may be accomplished in relatively low, large diameter enclosures or flare structures. In the burning of such gaseous materials in the conventional manner, difliculty is experienced in providing access of suflicient quantities of air to accomplish complete combustion. As a result, whether burned in elevated flare stack structures or otherwise, the burning is usually accomplished by the formation of large quantities of heavy, sooty smoke. Whether this smoke is released at higher or lower levels, an undesirable pollution of the atmosphere is created in the vicinity of the burning operation. An additional objection to conventional burning methods and the means provided therefor is to be found in the luminosity of the flame produced. Both luminosity and smoke primarily are due to the presence of carbon particles which in the area of the flame are incandescent, and upon cooling at some distance from the point of ignition, form dense, sooty clouds of smoke.

In general, the prior art has suggested two methods of flaring and burning such gaseous materials. According to the one method, gas is discharged from the open upper end of a flare stack, without substantial premixing of air therewith, and ignited and burned at the point of discharge. Combustion of the discharged gases thus takes place in the ambient atmospheric air rather than as a combustible mixture of air and gas. Although a portion of the gas may burn immediately, a deficiency of oxygen induces carbon formation and especially where olefinic 2,971,605 Patented Feb. 14, 1961 ice that the heat generated by combustion of a portion of the gas stream may cause cracking of the unburned portions to form additional olefinic and paraflinic materials as well as carbon and hydrogen. At the same time, some molecules may polymerize to form long chain hydrocarbons. The combustion or partial combustion of such compounds increases carbon formation particularly in the presence of hydrogen and a reducing atmosphere.

The other most conventional method of burning combustible gaseous materials involves the adaptation of the principles of Bunsen or other similar gas burners. The use of flare stacks operated according to such principles has been largely unsuccessful for the reason that such type of operation requires that the gas be supplied to the burners at a substantially constant rate and high flow velocity in order .to prevent reverse flow of the combustible gas through the air induction inlets pro vided. Furthermore,'as the gases to be burned are usually exhaust gases from process equipment which must be released without substantial back pressure, they are usually discharged at pressures close to atmospheric pressure, and it would be impracticaland uneconomic to repressurize such gases once they had been released from the process pressures. Where air dilution or premixing of the gas stream with a forced air supply has been attempted, it has been found that the volume of air required plus the volume of combustible gas. to be burned would necessitate employment of flare stacks of excessively large diameter. For example, Whereas a conduit six inches in diameter would be adequate as a flare stack according to conventional procedures, to obtain an optimum flame condition by dilution of the gas with air prior to discharge of the gas from the stack, in the burning of eiich 1000 cubic feet of gas, provision would have to be made for the stack to handle about 6000 cubic feet of air per minute in addition. With such volumes of air and gas, the stack would have to be about sixteen inches in diameter. Inasmuch as the volumes of gas contemplated for disposal according to the present invention may be in excess of 2000 cubic feet per minute, combustion air at the rate of at least 12,000 cubic feet per minute would have to be handled by the stack in addition. Further, any system wherein the disposable gases were to be diluted with combustion air prior to flaring of the mixture would require an elaborate and expensive control system, and accordingly be most uneconomical.

Although it is also known that convection currents produced by burning gases in a stack, open to the atmosphere, may be employed to inspirate air to maintain combustion, difliculty has been experienced in attaining the flow of the large quantities of air required. Difliculty has also been experienced in obtaining adequate mixing or diffusion of gas in combustion air as required for smokeless burning. Still further where smokeless combustion of gases has been attempted by employment of systems in which combustion air has been inspirated by convection currents induced by burning the gases in a confined zone, difficulty has been experienced in maintaining the gas flame. With such large volumes of air required, high air flow velocities develop which tend to produce flame blow-out.

It is an object of the present invention to provide a method and means for substantially complete combustion of disposable gaseous material wherein combustion air is supplied to the combustion zone without forced feeding thereof. It is also an object of the present invention to provide such method and means wherein combustion air is inspirated into a relatively confined combustion zone at least in part by convection currents produced in the burning of the disposable gaseous materials. It is also complete combustion of such gaseous materials under circumstances in which the materials are burned by producing turbulent diifusion thereof into currents of combustion' air inspirated into a relatively confined combustion zone while substantially avoiding flame blow-out. A further object of the invention is to provide a method and means wherein combustion of the disposable gaseous materials is initiated in a relatively unconfined primary combustion zone, and completed without production of any substantial amount of smoke in a relatively confined or shielded secondary combustion zone spaced above the initial and primary combustion zone and in the presence 2 of an excess of combustion air. The invention and its objects may be more fully understood from the following description when read in conjunction with the accompanying drawings in which;

Figs. 1A and 1B, taken together, provide a showing of a system for flaring combustible gaseous materials according to the present invention, wherein Fig. 1A provides a view in vertical elevation of means for supplying such materials to a flare stack and burner means in such system shown in Fig. 1B as a view in horizontal section taken along the line II of Fig. 2;

Fig. 2 is a view in vertical section through a flare stack and burner means substantially as shown in Fig. 1, which section is taken along line II--II of Fig. 1;

Fig.v 3 is a view in vertical section through a portion of the flare stack and burner means as shown in Fig. 1, which view is diametrically of the stack toward either portion indicated in Fig. 1 by the letters A or B, and including a showing of three burner tubes and component parts in relation to such portion;

Fig. 4 is a view in vertical transverse section of two adjoining modified burner tubes according to the present invention;

Fig. 5 is a view in vertical transverse section of two adjoining burner tubes illustrating another modified form of burner tube according to the present invention; and

Fig. 6 is a view in vertical transverse section of two adjoining burner tubes illustrating still another modified form of burner tube according to the present invention.

Referring to the drawings in greater detail, in Fig. 1A, the numeral 1 designates a conduit for disposable and combustible gaseous materials, which conduit may be connected to one or more sources of such materials. In the drawing, the conduit I typically represents a twelve inch diameter conduit. The numerals 2 and 3 designate branch conduits from the conduit I, typically of eight inch and ten inch diameter respectively. The conduit 2 extends into a horizontal seal drum 4 to terminate below the surface level of a body of seal liquid S-maintained therein at the level of an overflow weir 6. In the apparatus as shown, a conduit line 7 provides a liquid seal for the drum and for drainage of overflow seal liquid from the drum 4 and includes a vacuum breaker 8. The valved conduit connections 9 and 10 provide for complete drainage of the drum 4, while valved conduit connection 11 provides for initial or supplemental supply of seal liquid thereto. The conduit connection 12 communicating with the upper portion of the drum 4 above the level of seal liquid therein provides for release of gaseous material from the drum 4.

v The branch conduit 3 communicates with a second, seal drum 14. As shown, this drum 14 is disposed in a vertical position, and the conduit 3 extends downwardly thereinto through the upper end of the drum to terminate below the surface level of a body of seal liquid 15 maintained at the level of an overflow weir 16. A conduit line 17, including a vacuum breaker 18 provides a liquid seal for the drum 14 for drainage of overflow seal liquid. Valved conduit connections 19 and 20 permit complete drainage of seal liquid from the drum 14, while valved conduit connection 21 provides for initial and supplemental supply of seal liquid to the 1 T 0ndl it connection 22, communicating with the upper portion of drum 14, above the seal liquid level therein, provides for discharge of gaseous material from the drum. Where the inlet conduits 2 and 3 are eight inch and ten inch conduits respectively, the outlet conduits 12 and 22 should have corresponding dimensions.

In addition to their other conventional functions, the seal drums 4 and 14, and the inlet conduits 2 and 3 provide means for controlling gas flow from the conduit 1 to gas disposal means later described. -Such control is accomplished by disposing the terminalend of the conduit 2 in drum 4 at a distance below the upper edge of the overflow weir 6, which distance is less than that between the terminal end of conduit 3 and the upper edge of the overflow weir 16 in drum 14. In this way the hydrostatic head of seal liquid in drum 4 which resists flow of gas through the conduit 2 is less than the hydrostatic head of seal liquid in drum 14 which resists flow of gas through the conduit 3. Accordingly gas flow is preferentially directed through the conduit 2, drum 4 and conduit 12 until such time as the flow capacity of conduit 2 is exceeded. The resulting increase in gas I pressure in the conduit 1 will then overcome the greater hydrostatic pressure head on conduit 3, and under this pressure gas from line 1 is also released through conduit 3, drum 14, and conduit 22.

Fig. 1B includes a cross sectional view through a secondary combustion zone as provided by means of a stack 31, and also a plan view of a .burner layout according to the present invention. The stack 31 is represented as comprising a tubular steel she'll 31a which is lined with a heat resistant liner material 31b, such as a refractory material. The secondary combustion zone as shown is defined by the open ended stack chamber 31c. The refractory material may include pre-cast refractories, or a refractory material applied to the inner surfaces of the stack as a substantially continuous coating. In any event it is contemplated that the refractory material employed shall be light in weight, resistant to thermal shock, and of a nature and thickness adequate to maintain the operating temperature of the shell 31a at less than 900 F.

The capacity of the stack 31 to provide for smokeless flaring of gaseous materials is substantially determined by a relationship between its volume and the anticipated maximum flow rate of the gaseous materials to be burned. Inasmuch as it is an object of the invention to limit the total height of the structure required, the desired relationship is attained by variation of the stack diameter and thereby the cross-sectional area of the stack; Preferably the vertical dimension of the stack should be not less than that required to avoid visible emergence of the secondary combustion flame from the upper end of the stack. At maximum flow rates the maximum height of this flame is desired to be limited to about twentyfive feet. Using a thirty-two foot stack flame emergence may be obviated, if the stack cross-sectional area is established at about 50.0 square feet for each million standard cubic feet per day of burnable gas-flow. With this relationship, the stack capacity is adequate to handle both the burnable gas and primary combustion gases, as well as more than 60% excess secondary combustion air. This relationship further permits operation with gas flow as low as less than the anticipated maximum flow rate, while retaining satisfactory operating characteristics. and without total flame extinguishment. The gas flow turn down ratio of about 10 to 1 is achieved by means of the seal drum arrangement as shown, greater ratios may be attained by additional drums and further division of their discharge among the tubes of the burner grid provided.

The stack 31 is elevated and supported, as by column supports 32, in vertically spaced relation above a base plane, and above a grid comprising tubes or conduits 13, 23, 24, and 25, T e grid tube 13 is disposed in diametric :screen designated by the numeral 28. The nature ,25, burner nozzles 26 and flame-holders 27' relation to the stack, while grid tubes 25 are chordally related thereto, and in substantially parallel co-planar relation to the tube 13. The conduits 23 and 24 are disposed in substantially parallel relation to each other and right angular relation to the tubes 25. The latter are connected at their ends in communication between the conduits 23 and 24.

The conduits 23 and 24 are header conduits, of which one, as 23 in the drawing, is connected in communication with the conduit 22, the other header conduit, as 24 in the drawing, acting as a balancing line for the conduit grid system provided. The conduit 13 alone is connected in communication with the conduit 12, at one end, the opposite end being capped, or blanked off in some other fashion.

Preferably the conduit 13 has an inside diameter slightly smaller than that of the connecting conduit 12. The conduits 25 are of an inside diameter equal to that of conduit 13. The header conduits 23 and 24 in the preferred construction will have an inside diameter equal to that of the conduit 22. The parallel conduits 13 and 25 in the conduit grid system provided are disposed in equidistant relation.

Means for discharging disposable gaseous materials upwardly from the several conduits 13 and 25 are provided by burner nozzles 26. These nozzles are more clearly illustrated in Figs. 2 and 3. In the form illustrated by Figs. 1B, 2 and 3, the burner nozzles comprise short conduit sections, or pipe nipples of uniform dimensions, welded to the upper surface of the grid conduits 13 and 25, around passageways of corresponding diameter defined in the conduit walls to extend vertically upward therefrom. A series of such nozzles is provided for each grid conduit 13 and 25, the number in each series being determined by the length of each tube which is exposed within the area defined by the stack inner wall, by the diameter of the burner nozzles, and also as required substantially to avoid generalized merging of the nozzle discharge streams in the immediate vicinity of the nozzles. Preferably, the nozzles are also disposed so as to provide a substantially uniform arrangement or pattern. An acceptable arrangement is illustrated by Fig. 1B, wherein the nozzles are disposed in a pattern having a square pitch. In an alternate arrangement, the pattern may have a triangular pitch. The two nozzles at the outermost ends of the series associated with the conduit 13 are exceptions. These two nozzles are closer to their respective next adjoining counterparts, and also to the inner wall of the stack. This exception is for the purpose of facilitating ignition in the manner and by means such as later described. Ignition means such as contemplated and later described may be disposed in either or both the stack wall areas designated A and B in the drawing, and which are located at opposite ends of the tube 13.

A special feature of the burner construction contemplated according to the present invention comprises a flame-holder adapted to overcome the tendency of the combustion air, flowing upward between the grid conduits,

to lift the flame of burning gas from the burner nozzle with a consequent liklihood of extinguishment of the vlame. Such flame-holder means are shown in greater detail by Figs. 2, 3, 4, 5 and 6 and more particularly described below with reference thereto. In Fig. 1B, the flame-holder means are indicated by the reference numeral 27. Also appearing in the view of the structure provided by Fig. 1B, is the upper edge of a louvered wind of this wind screen is more clearly illustrated by Fig. 2, and its function is described with reference thereto.

In the sectional view provided by Fig. 2, the nature, association and relationships of burner grid tubes 13 and are shown in greater detail, as is the wind screen 28. In the form shown by Fig. 2, andalso by Fig. 3, the flame-holders 27 army he tubes, pipes or cylindrical rods, each having a 6 diameter substantially equal to the inside diameter ofa nozzle 26. Although as shown a flame-holder of cylindrical form is preferred, other shapes may be used provided the desired function is served. In any form the flame-holders 27 are supported in coextensive relation to a burner tube, diametrically of the series of burner tube nozzles, and at a distance vertically thereabove which is substantially equal to the inside diameter of a nozzle tube. The inside diameter of the nozzle tubes, and the diameter of the passageways in burner'tubes 13 and 25, are preferably in the range of from about 0.5 inch to about 1.0 inch. The wind screen 28 is of a substantially conventional form, being extended upward from the base plane or ground level to a level sufficiently above the lower end of the stack 31, and the burner grid structure to prevent direct access of atmospheric air currents to the flames produced by ignition of the gaseous materials discharged by nozzles 26. Also as illustrated in the louvered screen 28, the individual louver elements 28a are arranged to incline downwardly toward the surface area enclosed, whereby air currents through the screen tend further to be dispersed. Six inch louvers, disposed at an angle of 45, and spaced at a surface to surface distance of about three inches provide a preferred form of construction.

Fig. 2 further affords a showing of the relative association of the burner grid with the secondary combustion chamber, designated in this figure by the numeral 33. In this view of the apparatus the separate discharge streams of gaseous materials from the nozzles 26 are indicated by arrow tipped sinuous lines, while an induced flow of combustion air is indicated by heavier arrow tipped curved lines. A primary turbulent combustion zone in the immediate vicinity above .the burner conduits and nozzles is also indicated and designated by the numeral 34, and a representative outline of the combustion flame in the secondary combustion zone is provided by a broken line. The flame holding function of the elements 27 is achieved in the structure of Fig. 2, by partial dispersal of the gas issuing from the nozzles 26, and by producing a zone of turbulence above the elements 27'.

The ignitor means, previously referred to in the description of Fig. 1B asdisposed in the areas A and B of the stack 31, and at the bottom end thereof, are shown in greater detail in the view provided by Fig. 3. In Fig. 3, the numeral 41 designates a panel insert portion partially within and partially dependent below the wall of the stack 31. As shown, the insert comprises a pair of inset angular mufile blocks 42 and 43 disposed in laterally spaced relation, and with the insert in place, opening angularly toward a nozzle 26 on the first stage burner tube 13, which nozzle is at an outer end of the series of nozzles on that tube and next adjacent the inner wall of the stack.

Each of the muffle blocks 42 and 43 provides a recess portion 42a and 43a respectively into which is extended a fuel supply tube and pilot burner nozzle. Of these tubes and nozzles, the one designated by the numeral 44 in the drawing is an oil pilot burner while the other designated by the numeral 45 in the drawing is a gas pilot burner nozzle. The projected center lines through mufile blocks 42 and 43 and the nozzles 44 and 45 substantially will intersect at a point common to the center line of the burner tube nozzle 26 on the burner tube 13, which burner .tube nozzle is closest to the inner wall of the stack 31. In line with the two nozzles 44 and 45, at the same level, and midway between them in the insert portion is a pilot ignition burner 46. Preferably this is a fish tail burner nozzle adapted to provide a flame pattern which will substantially intercept a projection of the axis of each of the burner nozzles 44 and 45. Vertically aligned with the nozzle 46 and in spaced relation below it, a tubular passageway 47 provides means for insertion of a flame or sparking means from the exterior of the stack in order to ignite a flammable fuel stream 7 discharged from the fish tail burner. The fish tail burner .flame then serves to ignite either or both of the pilot burners, which in turn are adapted to project a flame over the adjacent discharge nozzle 26 of the burner tube 13 to ignite gaseous materials issuing therefrom.

.The showing of Fig. 3 also serves further to indicate the vertically spaced relationship between the burner tube grid and the lower end of the stack 31. In a typical installation wherein the stack inside diameter was about 6 feet, the burner tube grid was disposed so as to provide a vertical distance of approximately 6.5 inches between the discharge end of the burner tube nozzlesand a horizontal plane common to the lower end of the stack 31. Preferably the grid system should be disposed so as to provide vertical distance between the nozzle discharge ends and the lower end of the stack in the range of from about 3.5 inches to about 7.0 inches. In another typical installation employing a stack having an inside diameter of about 12 feet, the distance was de termined at about 7.0 inches.

Fig. 4 illustrates an alternate form of a flame-holder element as applied to typical tubes 13 and 23. In this form of the device, the discharge passageways for disposablegas, such as designated in the drawing by the numeral 36, substantially are simple circular cut out portions in the upper surface area of the burner tube, centered in a vertical plane longitudinally of the tube. These passageways are substantial equivalents of those described with reference to Figs. 1 and 2, the jet discharge nozzles 26 having been omitted. In the modified form also, the flame-holder. provided comprises an elongated angular strip or shape 37 attached to the upper surface of. the burner tube 23 at its vertex edge portion by any convenient means such as welds 38. Preferably, the strip 37 forms an angle which is slightly less than 90 but other angular shapes may be employed. In such flame-..

holder device, the leg portions of the angle are pref erably dimensioned so that when the angle strip is attached to the burner tube in the manner shown, these leg portions extend upwardly and outwardly slightly beyond the. peripheral edge of the passageways 36. In the drawing, sinuous arrows provide representative illustration of the combined dispersal effect on a gaseous material discharged from the burner tube passageways 36 into a stream of atmospheric air flowing upwardly between the tubes, and around the discharge passageway 36. As indicated, a zone of turbulence is produced in the region above the angular strip 37. Atmospheric air.

is incorporated or mixed with the discharged gaseous material in this zone, as well as in the areasadjace'nt to it, in order to provide .a combustible mixture. The angle strip also serves as a flame-holder and prevents lifting of the flame from the immediate vicinity of the discharge passageway thereby to cause extinguishment of the flame in the rising streams of atmospheric air.

In the form of the burner illustrated by Fig. 5, burner tubes comparable to the tubes 13 and 25 in Figs. 1B,

' are arranged in spaced relation one to another longitudinally of the tube. In any onetnbe, the passageways defined in one wall portion may be aligned in coaxial relationship to corresponding passageways defined in the opposite wall portion of the tube. Alternately, the series of passageways defined in one wall portion of a tube may be in staggered relation to the corresponding series of passageways in the opposite wall portion of the same tube.

From tube to tube, however, it is intended that each passageway defined in one tube shall be substantially coaxially related to a corresponding passageway defined in a wall portion of a next adjoining tube. In this way, the streams of gaseous materials issuing from the passageways in one tube will be opposed by similar and corresponding streams issuing from a corresponding passageway defined in the adjoining tube. Preferably the tubes in the burner grid system provided will be arranged in such parallel and laterally spaced relation that opposed streams of gaseous material discharged from adjoining tubes will meet in substantially impinging contact whereby intermingling of the opposed streams will produce some degree of turbulence in the area between adjoining holding function of the elements 27 or 37 identified above.

Fig. 6 illustrates another modification of the apparatus contemplated which is quite comparable to the modification illustrated by Fig. 5. In Fig. 6 the grid system burner tubes are designated by the numerals 63 and 65. These tubes compare with the tubes 53 and 55 of Fig. 5 and the tubes 13 and 25 of Figs. 1B, 2 and 3. In this modification, each tube is provided with a double row of passageways 66 which are defined in each tube wall to open radially outward therethrough with one row of passageways on each side of a vertical plane extended longitudinally of the tube and common to a diameter thereof. In each. row, the series of passageways provided are disposedin spaced relation one to another, each passageway opening upwardly along on a central axis common to a radius of the tube and inclined at an angle of about 45 with reference to a horizontal plane common to a. diameter of the tube. I Also, as described with reference to Fig. 5, the passageways 66 of any one series in any one tube either may be aligned with the passageways in the other series in that tube, or may have a staggered relationship thereto. In either event, however, from tube to tube, the passageways will be related so that a stream of gaseous material discharged from a passageway in one tube will substantially impinge upon a stream of gaseous materials discharged from a corre sponding passageway defined in the next adjoining tube. In effect in either form of the apparatus illustrated by Figs. 5 and 6 respectively, the impinging. streams of gaseous materials meet or intersect at an angle which is substantially twice the angle by which the axis of any individual passageway is related to a vertical plane common to a diameter of the tube. In the arrangement provided as shown by Fig. 6, substantially similar dispersion and flame holding functions are accomplished by the illustrated relationship of any two passageways in ad joining tubes. In each of Figs. 5 and 6 sinuous arrowtipped lines indicate the flow of gaseous materials issuing from the passageways 56 and 66, as well as the turbulence of the combining streams of gaseous materials andcombustion air. Likewise in each of these figures, the flow of combustion air into the areas of dispersion and turbulence is indicated by heavier arrow-tipped curved lines.

Operation of the apparatus according to the present invention may be best described with reference to the apparatus as in Figs. 1A, 1B, 2 and 3 of the drawings. In such operations the gaseous materials to be flared are initially'introduced into the system by way of the conduit 1 which may be considered as serving the function of a general collection means for the system being connected by various branch lines not shown to miscellaneous sources of gaseous materials to be disposed of by flaring.

When gaseous materials are present in the conduit 1 at a pressure suilicient to overcome the head of seal liquid above the lower end of the conduit 2, these gaseous materials will flow through the conduit 2 into the drum 4 to be discharged theretrom by way of the conduit 12 and the burner tube, grid system conduit designated in the drawings by the numeral 13. From the conduit 13, these materials will be discharged by way of the nozzles 26. The nozzle discharge streams contacting the flameholder element 27 associated with the tube 13 in the manner shown by the drawings is substantially dispersed along and over the element 27 whereby to establish a turbulent zone in the immediate vicinity of the element 27. With gaseous materials being discharged in such manner they may be ignited by either or both of the pilot flames provided by the nozzles 44 and 45, and at either or both ends of the tube 13, initial lighting of the pilot flames having been previously described.

Ignition of the streams of gaseous materials discharged by way of the nozzles 26 takes place in the dispersed discharge stream from either or both of the nozzles at opposite ends of the burner tube 13 which are next adjacent to the wall of the stack 31. Then, as a result of the dispersal elfect of the flame-holder 27, ignition will spread from one nozzle-stream to another in the series provided by the tube 13.

So long as the volume of gas flow through the conduit 1 does not exceed the capacity of the conduit system including branch conduit 2, the burner nozzles communicating with the grid conduit 13, and the intermediate portions of the flow line, flaring of the disposable gaseous materials will be accomplished through the grid conduit 13 alone. In the event, however, that the volume of gaseous materials entering the conduit 1 increases beyond the capacity of the first burner stage including the conduit system communicating with the burner tube 13, the back pressure produced in the conduit 1 will act to overcome the static pressure of the head of seal liquid above the lower end of the branch conduit 3 within the drum 14. Gaseous materials will then flow through the branch conduit 3 and the drum 14 into the discharge conduit 22 and thence through the header conduit 23 to be distributed and discharged by way of the several grid tubes 25 and the nozzles 26 communicating therewith. By means of the balancing header conduit 24, discharge of gaseous materials through the various burner nozzles in the grid system of tubes 25 is substantially equalized over the entire grid system. As the pressure in the conduit 1 is thus relieved through the second burner stage of the system, the gaseous materials discharged will be ignited from the dispersed and burning streams issuing from the nozzles communicating with the burner tube 13.

Ignition of the streams of gaseous material as discharged and dispersed in the immediate vicinity of the nozzles 26 produces convection currents of air from the ambient atmosphere to induce air flow upward between the tubes of the burner grid system into what may be termed a primary combustion zone around and immediately above the discharge nozzles. In this zone, turbulence of the dispersed streams produces at least a partial mixing of combustion air with the gaseous materials. The amount of air which may thus be incorporated in the burning streams is relatively limited however, and normally will be less than required for complete combustion of the gaseous materials as discharged from the nozzles. In the combustion zone, relatively large amounts of unconsumed or partially consumed gaseous materials will exist. The convection currents created by such degree of combustion as takes place in the first zone induces a draft upwardly into the stack 31. By reason of the disposition of the burner grid in the manner previously described, i.e., in vertically spaced relation below the lower end of the stack, access to the stack for large volumes of secondary combustion air is provided. This air along with air passing upwardly between the burner tubes and the unconsumed gaseous materials as well as the products of partial combustion taking place in the primary combustion zone pass upwardly into the stack. Within the stack, this mixture of combustion air, gaseous materials and partial combustion products undergoes secondary combustion in the presence of an excess of air which may be in the range of from to or more. The stack defines a secondary combustion zone in which final and substantially complete combustion of all burnable material takes place.

In a specific example of the employment of an apparatus according to the present invention, a stack 6 feet in diameter and 32 feet high was mounted on supports so as to be disposed about 5 feet above ground level. A burner tube grid system was then supported below the lower end of the stack and spaced therefrom at a distance of about 12.5 inches. The grid system comprised a first stage burner tube such as the tube 13 in the drawings having a 3-inch inside diameter aligned in substantially parallel relation to a diameter of the stack. The remainder of the grid system comprised a pair of second stage burner tubes such as the tubes 25 in the drawings disposed one on each side of the first stage burner tube, in parallel, substantially coplanar relation thereto, and two additional second stage burner tubes, having an inside diameter of 2 inches, at each outer end of the grid system and in substantially parallel coplanar relation to the other tubes therein. All tubes in the grid system were spaced, one from another at a distance of about nine inches. Each of the second stage burner tubes was connected at one end to a header conduit such as the header conduit 23. This headerconduit had an inside diameter of 4 inches and was connected at one end to a source of supply for disposable gaseous materials. The first stage burner tube previously mentioned was 'con nected to the same supply source. Valves in the connection lines provided for flow control such as normally would be accomplished by means such 'as the seal drums shown in Fig. 1A of the drawings.

Each of the burner tubes, in the grid system provided, was drilled to define a series of passageways 0.5 inch in diameter opening radially through the tube walls, and vertically upward in substantially parallel relation to the axis of the stack. Discharge nozzles such as the nozzles indicated in the drawings by the numeral 26 were provided by means of 9 inch pipe sections, having internal diameters of 0.5 inch, affixed to the upper surface of each of the burner grid tubes surrounding the drilled passageways therein. In all, thirty-seven such passageways and discharge nozzles were provided of which seven were in each of the burner tubes forming the first stage burner corresponding to tube 13 in the drawings, and seven in each of the second stage burner tubes next adjoining the first stage tube. 0f the four remaining tubes in the grid tube system, the outermost tube at each side of the system was provided with three such passageways and discharge nozzles while the next adjoining tube to each was provided with five passageways and nozzles. All passageways and nozzles were within an area substantially defined by the inner periphery of the stack, and spaced one from another in a longitudinal series common to any tube at a distance of about nine inches. A flame-holder was provided for each series of nozzles on each burner tube by means of a pipe 0.5 inch in diameter supported substantially in coextensive relation to the burner tube, and in vertically spaced relation to) theupper ends of the nozzles, about 0.5 inch there a ove.

This apparatus of the specific example was employed 11 to flare and burn a refinery gas of typical composition as shown by the following analysis:

The gas had an average molecular weight of 40.

When this gas was burned by means of the apparatus described it was found that the gas could be flared at rates up to about 600,000 standard cubic feet per day without any substantial production of smoke at the outlet of the stack. Flaring and burning was accomplished also without appearance of flame at the stack outlet. The apparatus provided equally satisfactory combustion characteristics for the burning of the refinery gas stream at flow rates between about 60,000 and 600,000 standard cubic feet per day. In other words a 1 to turn down ratio was attained.

On subsequent operations, vertical relationship of the grid system to the inlet of the stack was varied to es-' tablish the discharge ends of the nozzle tubes at distances of 6.5 and 7.0 inches below the stack inlet. In each instance the operating characteristics remained substantially comparable to those of the 3.5 inch spacing initially employed.

In another instance, a burner grid was modified to provide a total of nine nozzle tubes having an internal diameter of one inch, and arranged to provide nozzle tube spacing on about eighteen inch centers. With this arrangement of the grid and tubes, comparable flaring efficiency was obtained when the discharge ends of the nozzle tubes were disposed about 6.5 inches below the stack inlet, although the maximum flaring capacity of the apparatus was somewhat reduced.

Both flaring capacity and overall operating characteristics were seriously affected however when the grid was arranged so as to dispose the outlet ends of the nozzle tubes above the stack inlet end. For example, with the nozzle tubes disposed within the stack, and their discharge ends spaced six inches above the stack inlet, flaring capacity was reduced from a maximum rate of about 560,000 to about 500,000 standard cubic feet per day. The turn down ratio was also adversely afiected by this arrangement.

What is claimed is:

'1. A method of flaring combustible gaseous materials, comprising dividing an initial, confined stream of said materials into a plurality of confined, substantially coplanar, laterally spaced streams of lesser cross-section than said initial stream, discharging said streams of lesser cross-section upwardly into an ambient atmosphere of air as a plurality of jets spaced one from another longitudinally of each stream of lesser cross section and from stream to stream, dispersing a major portion of each of said jets angularly outward and upward therefrom into an initial combustion zone substantially intermediate and immediately above said parallel, confined streams of lesser cross-section, and upwardly therefrom as a partially consumed, turbulent mixture of said gaseous materials with air from said ambient atmosphere thereof, into a vertically defined secondary combustion zone in pheric air while encompassing the overall area of said jets and extending upwardly from an inlet to said secondary zone at a level spaced above the level of dispersion of said jets, admitting air from said ambient atmosphere to said secondary combustion zone through, around and over said initial combustion zone, and igniting said jets of said combustible, gaseous materials in the vicinity of discharge from said parallel streams.

2. A method of flaring combustible, gaseous materials, comprising dividing an initial, confined stream of said materials into a plurality of confined, substantially coplanar, laterally spaced, parallel streams of lesser crosssection than said initial stream, discharging said streams of lesser cross-section into an ambient atmosphere of air as a plurality of jetted streams of further reduced crosssection, and in a spaced pattern in a substantially common plane, dispersing the gaseous materials thus discharged to form an unconfined turbulent mixture of said materials in the ambient air in the immediate vicinity of said jet streams, igniting said mixture in the vicinity of said jet streams, whereby said gaseous mixture is at least partially consumed in an initial, unconfined combustion zone in the immediate vicinity of said jet streams, inducing upward convection gas flow currents by the heat of combustion from said initial combustion zone, passing combustion products, unconsumed gaseous materials and an excess of combustion air from the ambient atmosphere of said initial combustion zone upwardly into a second, confined vertically extending combustion zone in open communication at each end with ambient atmospheric air, regulating the discharge of said gaseous materials to a flow rate thereof in the range between about 20,000 cubic feet per day and about 2,000 cubic feet per day for each square foot of the cross-sectional area of said secondary combustion zone, and substantially completing combustion of said discharged gaseous materials within the vertical limits of said second zone.

3. An apparatus for flaring combustible, gaseous materials, comprising a stack structure open at both ends to ambient atmospheric air, disposed in elevated, vertically spaced relation to a substantially horizontal support base therefore, said stack defining a vertically and laterally defined secondary combustion chamber in open communication at each end with an ambient atmosphere of air, said stack having a lower end, a bank of discharge conduits for said gaseous materials disposed in substantially parallel, coplanar, laterally spaced relation in a. primary, substantially unconfined, combustion zone below the lower end of said stack, and at a level intermediate said lower end and said support base, means for discharging gaseous materials conveyed through said bank of discharge conduits as a plurality of jets thereof so as to be passed upwardly through said primary combustion zone toward the lower end of said stack, means for dispersing said jets of the gaseous materials, and means for igniting said gaseous materials in said primary combustion zone, immediately adjacent said discharge and dispersion means for said jets of gaseous materials.

4. An apparatus according to claim 3, wherein said bank of conduits comprises a pair of header conduits spaced apart in coplanar relation, of which a first header of said pair is connected by conduit means to a supply source of combustible gaseous materials, a plurality of discharge conduits extended in right angular relation to each of said pair of header conduits and communicating between them, and a single discharge conduit in said bank separately connected to said supply source, said discharge conduits being disposed in an area substantially defined within the peripheral limits of the cross-sectional area of said stack.

5. An apparatus according to claim 3, wherein said means for discharging gaseous materials from said bank of conduits comprises a plurality of narrowly defined jet stream passageways communicating with and opening open communication at each end with ambient atmos- 18 radially upwardly from each conduit in said bank of conduits, said passageways including several series of at least two passageways each, wherein each series communicates with one of said conduits and wherein said passageways in each series are disposed in spaced relation to each other longitudinally of said one conduit.

6. An apparatus according to claim 5, wherein said jet stream passageways are defined by means of pipe sections having inner ends connected to said discharge conduits in right angular radial relation thereto and communicating at their inner ends with said discharge conduits to which they are thus connected.

7. An apparatus according to claim 5, wherein said jet stream passageways are defined in and open radially through the walls of said discharge conduits.

8. An apparatus according to claim 5, wherein said jet stream passageways are disposed in a geometrical pattern wherein each passageway in each series is aligned with corresponding passageways in an adjoining series.

9. An apparatus according to claim 3, wherein said means for discharging said gaseous materials, and said means for dispersing said discharged jets of gaseous materials comprises a series of narrowly defined jet stream passageways communicating with and opening radially from each of said discharge conduits into individual, paired and substantially opposed discharge relation to the jet stream passageways of a corresponding series thereof opening from an adjoining discharge passageway, whereby said jet stream discharged from paired, opposed passageways are substantially dispersed by mutual impinging contact.

10. An apparatus according to claim 3, wherein said means for dispersing said jets of the gaseous materials comprises a plurality of cylindrical elements each substantially coextensive with one of said discharge conduits, and supported in vertically spaced relation to said discharged means and in a vertical plane extending sub- 14 stantially longitudinally and diametrically through said cylindrical element, and common to the axes of said plurality of jets.

11. An apparatus according to claim 3, wherein said means for dispersing said jets of the gaseous materials comprises a series of substantially V-shaped elements each mounted on and substantially coextensive with one of said discharge conduits and disposed with the apex edge of said element lying in a vertical plane extending through the axis of said discharge conduit and common to the axes of said plurality of jets.

12. An apparatus according to claim 4 wherein said conduit means connecting said first header to a supply source of gaseous materials includes a first liquid seal drum adapted to contain a body of a liquid seal material having an upper surface lever therein, and wherein said conduit means also includes an inlet conduit portion extended into said seal drum to a level substantially below that predetermined for said body of liquid, and wherein said single discharge conduit in said bank which is separately connected to said supply source includes a second liquid seal drum and inlet conduit portion therefor, substantially identical with said first drum.

References Cited in the file of this patent UNITED STATES PATENTS 1,688,641 Mackenzie Oct. 23, 1928 1,699,032 Shuell et a1. Jan. 15, 1929 1,775,565 Kessler Sept. 9, 1930 1,804,875 Hynes May 12, 1931 1,954,476 Gloekler Apr. 10, 1934 2,065,681 Fogas Dec. 29, 1936 2,656,008 Engel Oct. 20, 1953 2,752,870 Short et a1 July 3, 1956 2,792,070 Strunk May 14, 1957 

